Mike Duffy's Prince Edward Island Senate seat may not be safe yet, with sources telling CBC News the committee seeking legal advice on his residency has yet to receive a response.

Yesterday, Senate Government Leader Marjory LeBreton suggested the question was settled over whether Duffy, who lives mostly in Ottawa, was qualified to represent P.E.I. She pointed to a declaration of qualification document that all senators sign when they are appointed, which lists the senator's name, city and province.

"That's the document that secures your legitimacy to sit in the Senate," LeBreton told reporters Thursday.

Asked whether that was the answer to the legal opinion that had been sought over Duffy's residency, LeBreton suggested it was.

"There is no doubt that senators that sit in the Senate, by way of the declaration of qualification, qualify to sit in the Senate," she replied.

But sources have told the CBC's James Cudmore the legal opinion hasn't been provided yet to the committee on internal economy that was looking at where each senator lives.

On Friday, LeBreton said the committee "can only deal with the question of residency as it relates to the payment of expense claims."

"The intent of my answer was not to suggest that internal economy has a legal opinion. Internal economy can only deal with the question of residency as it relates to the payment of expense claims. Senator Duffy maintains a residence in P.E.I. and is qualified to sit in the Senate," she said.

4 senators to be audited

A spokeswoman for the Senate said she couldn't comment "on the ongoing work being undertaken."

The Senate internal economy committee asked all senators to prove they live where they say they do after media reports questioned whether Duffy, Quebec Senator Patrick Brazeau and Ontario Senator Mac Harb were collecting living expenses to which they weren't entitled.

Senators are eligible for up to $22,000 a year to cover the cost of living in Ottawa while the Senate is sitting, as long as their primary residence is more than 100 kilometres outside of the Ottawa-Gatineau area.

Because the Constitution says senators shall reside in the province from which they were appointed, more questions arose over the separate issue of whether Duffy was eligible for his seat. The internal economy committee asked for a legal opinion on that.

The committee reported back Thursday and said four senators have been referred for an external audit over their spending. Cudmore reports those senators are Duffy, Brazeau, Harb and Saskatchewan Senator Pamela Wallin.

with files from James Cudmore